CVE-2026-56743: Cilium is a networking, observability, and security solution

Routine

MEDIUM 5.4UPGRADE

CVE-2026-56743 is a medium-severity flaw (CVSS 5.4) affecting cilium. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Cilium is a networking, observability, and security solution. From 1.19.0 to 1.19.4, standard Kubernetes NetworkPolicy specifications using CIDR-based ipBlock rules without pod or namespace selectors erroneously generate a wildcard namespace allow rule when Cilium is configured with a custom clusterName rather than the default any value. The parser incorrectly instantiates a pod selector on selectorless peer definitions, allowing traffic from oth

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	5.4 (Medium)
Attack vector	Adjacent network
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.2% (top 84%)
CISA exploited list	No
Weakness	CWE-863
Published	2026-07-15
Last modified	2026-07-17

Publisher (CNA): GitHub, Inc. · Vendor: cilium

Last updated 2026-07-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-15 20:17 UTCPublished CVE record published
2026-07-17 17:29 UTCUpdated Record last modified

cilium cilium UPGRADE

Affected: >= 1.19.0 and < 1.19.5

Fixed in: 1.19.5

Safe to downgrade to: a release before 1.19.0

1. Check installed version

apt-cache policy cilium || rpm -q cilium || cilium --version

2. UPGRADE to 1.19.5 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade cilium

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade cilium

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 1.19.0 (Debian / Ubuntu)

apt-cache madison cilium sudo apt install cilium=<VERSION_BEFORE_1.19.0> sudo apt-mark hold cilium

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list cilium sudo dnf downgrade cilium-<VERSION_BEFORE_1.19.0> sudo dnf versionlock add cilium

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-56743?

cilium: upgrade to 1.19.5. Exact commands for each OS are on this page.

Is CVE-2026-56743 being exploited?

CVE-2026-56743 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-56743 affect?

CVE-2026-56743 affects cilium. Severity is medium (CVSS 5.4). Cilium is a networking, observability, and security solution. From 1.19.0 to 1.19.4, standard Kubernetes NetworkPolicy specifications using CIDR-based ipBlock rules without pod or namespace selectors erroneously generate a wildcard namespac

How urgent is CVE-2026-56743?

Priority 23/100. No elevated risk signals yet.

Software pages

Kubernetes vulnerabilities

Related CVEs

CVE-2026-49445 CRITICAL 9.2 UPGRADE Cilium is a networking, observability, and security solution
CVE-2026-56742 MEDIUM 5.9 UPGRADE Cilium is a networking, observability, and security solution

References

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